We follow the species order of R. P. Rossbach (1940). While there have been attempts to define species groups, and sections have been described, all such efforts focus only on European-Mediterranean taxa, ignoring the many taxa endemic to South America. Likewise, the major breaks in the key to species follow Rossbach's revision. Attempts to construct a key independent of habit were not successful; Spergularia is a difficult genus in which emphasis on seed characters appears necessary.

Spergularia is included in the first list of nomina genericorum conservanda published in 1905, conserved against Buda and Tissa. This action most likely occurred as a result of bickering between J. Britten and N. L. Britton in 1888-1890 about usage of the genera that Adanson had erected for Spergularia species with ten and five stamens respectively; see J. Britten (1890) for a summary of the arguments.